Winning the Water Industry Coarse Angling Championships is proof the Tees fish stocks are now thriving, according to environmental experts.

But some anglers claim the catch diverts attention away from the state of the river further upstream.

The championships are staged annually for staff from the country's ten water companies, British Waterways and the Environment Agency.

Twenty-five teams of 150 anglers will head for Teesside next month to fish the Tees between the A66 Tees Bridge and Preston Park.

The Environment Agency said the championships would be a good way of showing off the turnaround of the Tees.

EA team leader and match co-ordinator, John Shannon, said years of work by Northumbrian Water and the EA to cut discharges to the river meant there was now a thriving fish population.

"The completion of the Tees Barrage in 1995 created a 22km uniformly deep section of river upstream which was previously tidal and polluted," he said.

"As a result, over recent years there has been a very dramatic rise in its fish population, and it is now regarded as one of the north's premier river fishing venues."

But some fishermen from the river's middle reaches dispute that, saying EA estimations on fish numbers are flawed.

Some say brown trout and salmon haven't been seen in that part of the river for years and want a full-scale investigation into where the fish, which they say used to thrive in the river, have gone.

Don Taylor, who has fished the middle part of the river for almost five decades, said: "The Environment Agency may be only too happy to divert attention from the river's overall condition by publicising the match-fishing facilities in the lower reaches.

"That's a length that in effect is a long freshwater lake formed when the Barrage was built and ideal for coarse fish.

"But it in no way addresses the continuing problems in the middle reaches, particularly the critical level of brown trout stocks.

"Plus no migratory fish are being seen, despite the Agency's claims of many thousands of salmon and sea-trout running upstream to upper river spawning grounds."

An Environment Agency spokesman added: "There has actually been a gradual increase in salmon and trout in the River Tees since 1995 when the barrage was built.

"Since then there has been a year on year increase.

"The Agency does not feel the need to investigate, as all the trends show there is no problem."